Method of strengtherning a television display tube

ABSTRACT

A method of strengthening a cathode-ray tube against implosion in which a metal band and the conical portion of the cathode-ray tube adjoining the window are provided with an adhesive layer containing a reducing agent compatible with a redox system used to harden a combination of a polyester and a monomer. The metal band is placed around the conical portion of the tube and the space therebetween filled with a polyester, a monomer, a redox system, and a filler. The polyester mass is subsequently hardened at ambient temperatures.

United States Patent Inventor Floris DeBoer Emmasingle, Eindhoven,Netherlands a [21] AppLNo. 696,238

[22] Filed Jan. 8,1968

[45] Patented Jan. 26, 197] [73] Assignee U. S. Philips Corporation NewYork, N.Y.

a corporation of Delaware [32] Priority Jan. 18, 1967 [3 3 Netherlands[3 l 6700756 [54] METHOD OF STRENGTHENING A TELEVISION DISPLAY TUBE 3Claims, 1 Drawing Fig.

52 us. Cl l78/7.82, 220/2. 1 [51] Int. Cl ..H01j 29/28, HOlj 61/50,H0lk1/28 [50] Field ofSearch l78/7.82;

[56] References Cited UNITED STATES PATENTS 3,220,592 1 1/1965 Powelll78/7.82 3,412,203 1 III 968 DAngelo 220/2.1A

Primary ExaminerRobert L. Griffin Assistant ExaminerHoward W. BrittonAttorney-Frank R. Trifari ABSTRACT: A method of strengthening acathode-ray tube against implosion in which a metal band and the conicalportion of the cathode-ray tube adjoining the window are provided withan adhesive layer containing a reducing agent compatible with a redoxsystem used to harden a combination of a polyester and a monomer. Themetal band is placed around the conical portion of the tube and thespace therebetween filled with a polyester, a monomer, a redox system,and a filler The polyester mass is subsequently hardened at ambient temperatures.

'PATENTEU JAN 25 1971 INVENTOR.

FLORIS DE BDER BY v METHOD OF STRENGTHENING A TELEVISION DISPLAY TUBEThis invention relates to a method of strengthening a television displaytube with a substantially rectangular screen for the purpose of reducingthe risk of implosion. More particularly in accordance with theinvention the transition region between thewindow and the cone of thecompleted tube is surrounded by a metallic band so as to obtain a spaceof substantially wedge-shaped section between the whole or part of theinner surface of the band and the outer surface of the transitionregions. Thereafter this space is filled with a mixture consisting of anunsaturated polyester resin, a monomer which is polymerisable therewithand a filler. Subsequently, the mixture is hardened at room temperaturein a manner as is usable for this mixture with the aid of a redoxsystem. Part of the metallic band may be surrounded by further metallicbands under stress.

When using this method it is of essential importance for obtaining thedesired protection against implosion that satisfactory adhesion of thepolyester mass to the surface of the metallic band and to the surface ofthe glass forming the transition region is obtained. Only under theseconditions is it ensured that in case of cracks occurring in the windowowing to an external, mechanical cause, a mechanical stress exists ordevelops in the polyester-metallic band envelope wi which sufficientlycounteracts the implosion.

ln practice it has been been found that the difference between thecoefficients of expansion of the-metallic band and of the glass of thetransition region upon great variation in temperature cannot be bridged,unless use is made of expensive polyester resins specially developed forthis purpose.

For this reason the inner surface of the metallic band and the surfaceof the glass forming the transition region have previously been providedwith an adhesive layer of a thermoplastic synthetic material, moreparticularly polyvinylacetate.

In practice it is found that in this way a slight improvement isobtained.

However, upon close investigation it was found that with great variationin temperature, more particularly with cooling to temperatures down to-40 C., such as may occur during transport and storage in winter athigher degrees of latitude, the polyester mass locally loosens,resulting in superficial deterioration of the surface of the glass.

An object of the present invention is to provide a solution to thisproblem.

Mixtures of unsaturated polyester resins and monomers, such as styrene,which are polymerisable therewith, are hardened at room temperature withthe aid of a redox system consisting of an organic oxide and usually ametal soap or an amine as a reducing agent.

According to the invention the problem of obtaining satisfactoryadhesion was solved by using an adhesive layer containing a reducingagent of the kind which is also used in the redox system for hardeningthe polyester mass.

As such it is known to incorporate either the peroxide or the reducingagent in a primer layer which is covered with a layer of a mixtureconsisting of an unsaturated polyester and a monomer which ispolymerisable therewith and contains the other component of the redoxsystem. However, the primary object of this method is to preventpremature polymerisation of the mixture of unsaturated polyester andmonomer polymerisable therewith. If better adaptation of the shape of aninjection-moulded mass to the shape of the mould or better adhesion oflacquer layers should in this case be obtained, then the beginning ofthe polymerisation of the mass at the surface covered with primer layeris responsible for this.

However, in the method according to the invention, the polymerisationtakes place in the whole of the mass at the same time. Also, acontraction of the mass in the direction of the metal and glass surfacesdoes not occur. This contraction causes cracks in the mass, but suchcracks do not occur when the method according to the invention is used.

of materials.

The invention will now be described with reference to the accompanyingdrawing, the sale FlG. of which shows a part section of the marginalregion of a television display tube, and to the example to be describedhereinafter.

ln the sole FlG. the transition region between the conical part 2 andthe window 3 is indicated by l. A metallic band with a flanged part 5for fastening purposes is indicated by 4.

Starting with a 23 inch tube, the inner surface of the metallic band 4,(which is, for example, of aluminum) and the outer surface of thetransition region 1 are covered with 30 gm. of a polyvinyl acetatesolution consisting of 150 gm. of polyvinyl acetate, 1.5 liters of waterto which 1 percent by weight of dimethyl paratoluidine has been added.After the adhesive layers have been dried in air, the metallic band isplaced in a holder (now shown). Subsequently the completed televisiondisplay tube is placed in the metallic band in the manner shown in theFIG. The space of slightly wedge-shaped section between the band 4 andthe marginal region 1 is filled with a mass consisting of a mixturehaving the composition:

100 gm. of unsaturated polyester (for example type S 523) from SynresLtd. at Hook of Holland;

25 gm. of styrene;

90 gm. of filler (CaCO 5 gm. of benzyl peroxide;

0.35 gm. of dimethyl paratoluidine.

This composition may be used at a temperature of the working spacebetween 20 C. and 22C. At a higher temperature the amount of dimethylparatoluidine is reduced proportionately.

Comparative tests gave the following results:

If a polyvinyl acetate adhesive was used without an addition of adimethyl paratoluidine, the adhesion between the glass and the resin atthe comers of a substantially rectangular window was broken in more thanpercent of the cases even during the hardening of the polyester resin.

If dimethyl paratoluidine to an amount of 1 percent by weight was addedto the polyvinyl acetate adhesive, the said percentage decreased below 1percent.

The polyester resin used was of the general purpose type and consistedsubstantially of polyglycol-isophthalatemaleinate and styrene.

By the use of the invention a similar result was obtained as seemedpossible before only by using expensive polyesters, for example, on thebasis of neopentyl-glycol, which are specially manufactured for thispurpose.

The behavior of the tubes when cracks are caused in the glass by theaction of liquid air, during shock tests with a steel ball and incooling tests down to 40 C. was similar to that of tubes in which apolyester resin on the basis of neopentyl glycol had been used.

It will be evident that the invented method is not limited to theconstructions described nor to the specified combinations Evidentmodifications of the construction described in the example will be, forinstance;

a. The band 4 can embrace the tube over part of its width under stress.

b. The band 4, which may possibly consist of two parts can be surroundedby a clamping band after the resin has been poured in and hardened.

c. The band 4 may be positioned so that the aperture of the wedge-shapedspace 6 lies adjacent the window side 3 of the tube.

f. Other peroxides and accelerators can be used.

I claim:

1. A method of strengthening a television display tube having asubstantially rectangular window closing one end of a conical portionfor the purpose of reducing the risk of implosion comprising the stepsof applying to a surface of a metallic band and the surface of theconical portion adjoining the window an adhesive layer containing areducing agent for hardening a polyester mass, surrounding the conicalportion covered with said adhesive layer with said metallic band leavinga space therebetween, filling said space between the metallic band andthe conical portion with a mixture consisting of an the adhesive layeris the same as that in the redox system. unsalumtcfj Polyester a monomerwhich pllymcrlsa' 3. A method of strengthening a television display tubeas ble therewith, a redox system and a filler, and hardening the vclaimed |n claim 2 m WhlLh the reduemg agent is dimethyl mixture at roomtemperature. urlnoluidinc 2. A method of strengthening a televisiondisplay tube as 5 p i claimed in claim I in which the reducing agentcontained in

1. A method of strengthening a television display tube having asubstantially rectangular window closing one end of a conical portionfor the purpose of reducing the risk of implosion comprising the stepsof applying to a surface of a metallic band and the surface of theconical portion adjoining the window an adhesive layer containing areducing agent for hardening a polyester mass, surrounding the conicalportion covered with said adhesive layer with said metallic band leavinga space therebetween, filling said space between the metallic band andthe conical portion with a mixture consisting of an unsaturatedpolyester resin, a monomer which is polymerisable therewith, a redoxsystem and a filler, and hardening the mixture at room temperature.
 2. Amethod of strengthening a television display tube as claimed in claim 1in which the reducing agent contained in the adhesive layer is the sameas that in the redox system.
 3. A method of strengthening a televisiondisplay tube as claimed in claim 2 in which the reducing agent isdimethyl paratoluidine.